Especially in the field of truck cranes or also excavators there is a multitude of possibilities for hydraulic support, which serve to improve the load bearing capacity and the stability. Simple telescopable sliding beams, dual telescopable sliding beams, collapsible beams or also combinations of collabsible beams and sliding beams are known here, for instance.
Depending on the local conditions and in dependence on the required load bearing capacity, different conditions of extension of the sliding beams laterally extending from the chassis are required for a safe operation, wherein the load input into the sliding beams must be effected via defined load input points for static reasons. In all conditions of extension, it must be possible to reproducibly approach the load input points at any time.
It is already known to provide dual telescopable sliding beams, wherein the systems can be designed differently for telescoping out and retracting the sliding beams. In this case, the provided hydraulic cylinders and rope discharge systems can for instance be combined with each other. Instead of these systems, hydraulic cylinders with chain discharge have already been used. An alternative consists in using two hydraulic cylinders, one for each sliding beam, or to use a single two-stage cylinder.
In the known discharge system with one hydraulic cylinder and one rope or chain discharge, the telescoping operation of the sliding beams is effected as follows:
First of all, the first sliding beam is pushed out by means of a hydraulic cylinder between sliding beam box and sliding beam. The discharge of the second sliding beam is effected synchronously, as the same is mechanically connected with the first sliding beam via a hoist system comprising ropes or chains. In principle, the mechanical connection of the two sliding beams and the fixed length of the ropes or chains provides for a defined, always reproducible telescoping of the sliding beams up to the respective load input points of all conditions of extension.
In a discharge system with two hydraulic cylinders or one two-stage cylinder, the telescoping operation of the sliding beams is effected as follows:
Reference can be made to FIG. 1, which illustrates the basic structure of a corresponding telescopable sliding beam in accordance with the prior art. A sliding beam box 10 accommodates a first sliding beam 12 and a second sliding beam 14. Sliding beam box, first sliding beam and second sliding beam are each connected with each other via two hydraulic cylinders 16 and 18 to be pressurized with hydraulic pressure at the same time or via one two-stage hydraulic cylinder which is not shown here in FIG. 1 or FIG. 2. When the cylinders are pressurized with hydraulic pressure, the sliding beam with the lowest mechanical resistance will start to move first. While telescoping, the resistance in the bearing of the moving sliding beam will be increased. When the mechanical resistance of the moving sliding beam exceeds that of the still stationary sliding beam, the same will stop, and the sliding beam stationary so far will start to move. During a telescoping operation, this change of movement between the two sliding beams is repeatedly performed arbitrarily. Due to the changing mechanical resistances in the bearing of the sliding beam and the accordingly load-dependent telescoping of the sliding beams, a defined telescoping of the sliding beams up to the respective load input points cannot be effected under conditions of reduced extension.
Therefore, it is the object underlying the present disclosure to develop a generic telescopable sliding beam such that it can be telescoped out and retracted reproducibly, wherein in particular predetermined load input points can selectively be approached under conditions of reduced extension.
In accordance with the present disclosure, this object is solved by a telescopable sliding beam with a sliding beam box and at least one first and one second sliding beam, which are telescopable into each other, the first sliding beam being mounted in the sliding beam box such that it can be telescoped out. In accordance with the present disclosure, the first sliding beam can first be telescoped out to a desired point and then the second sliding beam can be telescoped out, whereas during the backward retraction, the second sliding beam can first be retracted to a desired point, and only then can the first sliding beam be retracted. The solution of the present disclosure is not restricted to two sliding beams. According to this solution principle, more than two sliding beams might form the telescopable sliding beam.
Accordingly, hydraulic cylinders are provided for telescoping out or retracting the sliding beams.
Particularly advantageously, a pressure sequence control is provided for the hydraulic cylinders. By means of the same, the first sliding beam in the first hydraulic cylinder is first extended in a controlled way, whereupon the second sliding beam is extended via a second hydraulic cylinder. During retraction, the second sliding beam is first retracted in a controlled way via the second hydraulic cylinder, whereupon the first sliding beam is retracted via the first hydraulic cylinder.
Advantageously, the pressure sequence control can be implemented by corresponding valves provided in the hydraulic conduits used for supplying the hydraulic cylinders.
Particularly advantageously, the telescopable sliding beams can be used in work machines, preferably truck cranes and excavators. Therefore, the present disclosure also relates to corresponding work machines 100 (see FIG. 3), preferably truck cranes and excavators, comprising at least one, but advantageously four corresponding telescopable sliding beams.